Maturation and longevity - Adults Fishes

Not surprisingly, age at first reproduction and longevity vary greatly among fishes (Finch 1990), making it difficult to identify patterns or draw conclusions .

Maturation and longevity

Not surprisingly, age at first reproduction and longevity vary greatly among fishes (Finch 1990), making it difficult to identify patterns or draw conclusions (for an excellent overview of various classifications of maturation stages, see Pusey et al. 2004, table 5). The adaptive signifi cance of differences in age at first reproduction relates to trade-offs between committing energy to somatic growth versus reproduction, combined with expected mortality rates and the probability of living long enough to reproduce. These trade-offs, Life histories and reproductive ecology. Extremes in age at first reproduction include some embiotocid surfperches, the males of which are born producing functional sperm. Gobioid fishes in the genera Schindleria and Paedogobius have been shown to mature in less than 2 months, Schindleria maturing in as little as 3 weeks (Kon & Yoshino 2002a). Many small stream fishes mature in 1 year, being reproductively active the spawning season after they hatch (e.g., most darters), although maturation may take longer in populations at higher latitudes.

At the other extreme, sturgeons and some sharks may take 10–20 years to mature. Sturgeons may live 80–150 years. The slowest maturing shark is the Spiny Dogfish, Squalus acanthias, a species well known to students of comparative anatomy. Spiny Dogfish do not mature until 20 years old and have the longest recorded life span of a shark, upwards of 70 years. The record for naturally delayed reproduction among bony fishes is apparently held by American eels in Nova Scotia, which may not mature and undertake their spawning migration back to the Sargasso Sea until they are 40 years old (see Catadromy).

Longevity patterns are only slightly more definable. With many exceptions, larger fishes generally live longer than smaller fishes. The oldest teleosts known are scorpaenid rockfishes of the northeastern Pacific. Radioisotopic and otolith analyses indicate that Rougheye Rockfish (Sebastes aleutianus) live for 140 years, Silver-gray Rockfish (S. borealis) for 120 years, and Deepwater Rockfish (S. alutus) for 90 years (Finch 1990; Leaman 1991). Among common sport species, European Perch can live 25 years and Largemouth Bass can live 15–24 years (Das 1994; Boschung & Mayden 2004).

Numerous species live for a year or less, including the so-called annual fishes of South America and Africa (see Deserts and other seasonally arid habitats). Several gobies have remarkably short generation times and life spans. The Australian coral reef goby Eviota sigillata spends 3 weeks as a planktonic larva, settles and matures within 1–2 weeks, and lives for no more than another 4 weeks, for a total life span of less than 60 days (Depczynski & Bellwood 2005). The shortest known life span among freshwater fishes occurs in an African rivuline, the nothobranchiid Nothobranchius furzeri, with a life expectancy in the wild of a few months and a maximum life span in the laboratory of less than 12 weeks (Valdesalicil & Cellerino 2003). Other short-lived species include North American minnows in the genus Pimephales (Fathead, Bullhead, and Bluntnose Minnows), several galaxiid fishes from Tasmania and New Zealand, retropinnid southern smelts, Japanese Ayu, Sundaland noodlefishes (Sundasalangidae), a silverside, and a stickleback.